The dependence upon the use of data networks to transmit and receive data at high data rates has led to a corresponding interest in the ability to perform real-time monitoring and analysis of that data, or network traffic, so that duplication of data as well as performance of the network can be evaluated, and problems identified and resolved. Such data monitoring and analysis necessitates the ability to access the network data stream without disrupting data transmission and the operation of the network.
To this end, monitoring systems utilizing network taps are employed which are configured so that network data can be captured for analysis without interrupting operation of the network. In general, such use various mechanisms to access network data. For example, some taps include a buffering mechanism that enables the capture of network data. In other cases, network taps are able to copy selected portions of the data stream, and then provide the copied portion of the data stream to a network analyzer or other device for evaluation.
Referring to FIG. 1, a conventional copper-based Ethernet monitoring system 100 is illustrated. For example, an Ethernet device 101 is shown as being in communication with an Ethernet device 102 using standard Cat5 network cable. As per the Gigabit Ethernet standard, the communication on the twisted pair cable is bidirectional as is depicted by arrows 110 and 111.
Also illustrated is a tap 120 which is situated in the communication path between Ethernet devices 101 and 102. Tap 120 is used to access the data signals for monitoring. The tap includes relays 121 and 122 that can direct the signal path flow.
Further included in system 100 are four Physical Interface Devices (Phys) 131-134. These Phys may be individuals or contained in two dual or one 130 quad IC package as shown. The Phys provide the physical connection between the copper Cat5 cable and the communication network.
In operation, when it is desirable to monitor the data flow between Ethernet devices 101 and 102, the relays 121 and 122 of tap 120 are energized causing the flow of information between Ethernet devices 101 and 102 to be redirected to Phys 132 and 133. For example, energized relay 121 causes the data from device A 101, referred to as A data, to flow to Phy 132. Phy 132 sends the A data signal to Phy 131, where it is provided to monitor A for monitoring and to Phy 133, which provides the A data to energized relay 122 and device B 102. In like manner, energized relay 122 causes data from device B 102, referred to as B data, to flow to Phy 133. Phy 133 sends the B data signal to Phy 134, where it is provided to monitor B for monitoring and to Phy 132, which provides the B data to energized relay 121 and device A 101. Accordingly, system 100, utilizing a tap 120 with a combination of relays 121, 122 and quad Phy 130, is able to monitor the communication between Ethernet devices A 101 and B 102 while still allowing the devices to communicate bi-directionally.
While system 100 has generally proven to be useful in enabling the monitoring and analysis of network traffic, significant problems remain with this conventional system. One problem of particular concern is that network tap 120 is often susceptible to a power loss or other fault conditions. For example, the external power supply to the network tap is a significant failure point in the system. Unfortunately, disconnection of such external power supplies is a relatively common occurrence. In many cases, disconnection of the external power supply to the network tap occurs because the network tap and power supply are located in a place where personnel may inadvertently, or mistakenly, unplug the power supply. These challenges are only magnified where multiple network taps are implemented in the communication network or other system.
Any loss of power or other fault typically causes relays 121 and 122 to close. Consequently, any A data and B data that would have passed through the relays 121 and 122 during the switching operation is lost. Also, any data that is in tap 120 and the quad Phy 130 when power is interrupted is also lost. In addition, Ethernet devices 101 and 102 must reconfigure themselves to properly communicate, which also disrupts network data flow. In view of the high data speeds employed in many networks, even a very short term interruption in power to the network tap 120 will seriously compromise the integrity of the data stream, so that even if the network is otherwise in operational condition, an interruption of power to the network tap and the resulting loss of data can severely impair operation of the network. This lack of fault tolerance in many high speed data communication network taps is a major concern that remains largely unaddressed.